The subject improvement relates to centralizers or centralizing devices operative to locate a casing or pipe string concentrically within a well bore or another casing. It is particularly directed to a non-weld centralizer which can be packaged in originally disassembled form for space-efficient shipping and easily and conveniently finally assembled in the shop or place of business of the purchaser or actually on the job site.
Typically, centralizing devices generally comprise upper and lower collar members adapted to removably encircle and embrace a casing or pipe, the collar members having a plurality of outwardly bowed spring members attached at the upper and lower ends thereof in various manners or ways to the collars. Such collars conventionally and conveniently are constructed of two or more arcuate sections with means of various types provided for joining the arcuate sections together after such are placed around a pipe or casing. Hinge and latch are typical. The spring members may be welded to the collar sections or mechanically attached thereto by various means and devices.
In actual use, centralizers are ordinarily supported on a pipe or casing at vertically spaced locations along its length. The outwardly bowed spring members yieldably engage the well bore or the inside surface of other casings circumferential thereto at spaced locations therealong. The well pipe may be a casing disposed within an open well bore or within another casing in the wellbore which, when centered, permits a uniform column of cement to be pumped into the annular space between it and what surrounds it.
When mounted on a pipe or casing section, centralizers are typically supported for limited endwise movement by one or more stop collars, the latter fixedly clamped or attached about the pipe or casing. A pair of such collars may be attached to the casing above and below the centralizer collars or a single stop collar may be clamped or otherwise attached to the casing intermediate the centralizer collar sleeve ends or both. In either case, the stop collars or stop members are so located with respect to the centralizer collars that the latter are freed to move towards and away from one another as the bowed springs expand and contract. This permits the centralizers to function in well bores of somewhat different diameters.
A major factor in the design of many centralizers is the manner in which the bowed spring members are connected or connectible to the end collars of the centralizer. Such connection governs the manner in which the centralizers may be originally assembled, whether only by the manufacturer at the place of manufacture or at a purchaser's shop, a field installation, on the job site, etc. The key difference is whether the centralizing device parts are originally fully assembled at the place of manufacture or manufactured and prepared in a state of disassembly for shipping to a spot for assembly away from the point of manufacture.
Clearly, a fully assembled centralizer occupies a relatively great volume of space compared to the volume required for its component parts nested or packed in sets for shipping. Thus, in order to minimize the shipping costs of centralizers to distant locations, non-weld centralizer or centralizers that are easily entirely or partially assemblable by the purchaser in his facilities or in the field have been developed. Many prior such designs have been provided, some of which are noted in the Prior Art section given herebelow.
A basic factor with respect to any centralizer construction, however, is that it must be not only structurally sound when assembled, it must also be sufficiently strong, once assembled, that it will effectively function in the well bore environment and not be easily damaged by the rough treatment normally encountered in well bore use.
Another important factor which is frequently not sufficiently considered in other centralizer designs or not present or allowed for in other centralizer designs is that the crew on the job site or at the assembly point may be laboring under such job site and assembly point conditions as will preclude sophisticated handling of complexly shaped pieces. Still further, job site or assembly point personnel may be generally relatively unsophisticated with respect to complex apparatus assembly. It follows, that, in order to be effective and useful in its job, a centralizer which is assembleable away from the point of manufacture or on the job site should be of extremely simple construction and assembleable in a manner that does not heavily tax either the facilities or skills of the job site personnel.